Geochemistry of highly depleted peridotites of the Mid-Atlantic Ridge
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| Natura: | Dataset Open Access |
| Lingua: | en |
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PANGAEA
2008
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| _version_ | 1867170454780772352 |
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| author | Godard, Marguerite Lagabrielle, Yves Alard, Olivier Harvey, Jason |
| author_facet | Godard, Marguerite Lagabrielle, Yves Alard, Olivier Harvey, Jason |
| collection | Datos científicos de ciencias marinas y ambientales |
| contents | During ODP Leg 209, a magma-starved area of the Mid-Atlantic Ridge (MAR) was drilled in the vicinity of the Fifteen-Twenty Fracture Zone (FZ) that offsets one of the slowest portions of the spreading ridge. We present here the results of a bulk rock multi-elemental study of 27 peridotites drilled at Sites 1272 and 1274 (to the south and the north of the FZ, respectively). The peridotites comprise mainly of harzburgites with minor dunites. Clinopyroxene (Cpx), which is interstitial and interpreted as secondary, is observed in Site 1274 peridotites. Sites 1272 and 1274 peridotites have low Al2O3 contents (<1 anhydrous wt.%), high Mg# (>91.5), and bulk rock trace elements compositions mostly below 0.1X primitive mantle (PM). These peridotites, and in particular Site 1272 peridotites, represent the most depleted peridotites yet sampled at a slow spreading ridge. Their compositions indicate high degrees of partial melting and melt extraction. A single open-system melting event (melting plus percolation of melts produced within upwelling mantle) can explain their highly depleted yet linear chondrite-normalized REE patterns, characterized by a steady depletion from HREE to LREE. Late melt-rock reactions and precipitation of Cpx explains the slightly less depleted compositions of Site 1274 peridotites. Hence, the differences in composition between Sites 1272 and 1274 peridotites do not provide evidence for regional variations in the degrees of partial melting from the south to the north of the FZ. The occurrence of highly refractory peridotites in the Fifteen-Twenty area suggests we sampled a more actively convecting mantle than generally supposed below slow spreading centers. |
| format | Dataset Open Access |
| id | pangaea_https___doi_org_10_1594_PANGAEA_707023 |
| institution | PANGAEA |
| language | en |
| publishDate | 2008 |
| publisher | PANGAEA |
| record_format | pangaea |
| spellingShingle | Geochemistry of highly depleted peridotites of the Mid-Atlantic Ridge Godard, Marguerite Lagabrielle, Yves Alard, Olivier Harvey, Jason 209-1272A; 209-1274A; DRILL; Drilling/drill rig; Joides Resolution; Leg209; North Atlantic Ocean; Ocean Drilling Program; ODP During ODP Leg 209, a magma-starved area of the Mid-Atlantic Ridge (MAR) was drilled in the vicinity of the Fifteen-Twenty Fracture Zone (FZ) that offsets one of the slowest portions of the spreading ridge. We present here the results of a bulk rock multi-elemental study of 27 peridotites drilled at Sites 1272 and 1274 (to the south and the north of the FZ, respectively). The peridotites comprise mainly of harzburgites with minor dunites. Clinopyroxene (Cpx), which is interstitial and interpreted as secondary, is observed in Site 1274 peridotites. Sites 1272 and 1274 peridotites have low Al2O3 contents (<1 anhydrous wt.%), high Mg# (>91.5), and bulk rock trace elements compositions mostly below 0.1X primitive mantle (PM). These peridotites, and in particular Site 1272 peridotites, represent the most depleted peridotites yet sampled at a slow spreading ridge. Their compositions indicate high degrees of partial melting and melt extraction. A single open-system melting event (melting plus percolation of melts produced within upwelling mantle) can explain their highly depleted yet linear chondrite-normalized REE patterns, characterized by a steady depletion from HREE to LREE. Late melt-rock reactions and precipitation of Cpx explains the slightly less depleted compositions of Site 1274 peridotites. Hence, the differences in composition between Sites 1272 and 1274 peridotites do not provide evidence for regional variations in the degrees of partial melting from the south to the north of the FZ. The occurrence of highly refractory peridotites in the Fifteen-Twenty area suggests we sampled a more actively convecting mantle than generally supposed below slow spreading centers. |
| title | Geochemistry of highly depleted peridotites of the Mid-Atlantic Ridge |
| topic | 209-1272A; 209-1274A; DRILL; Drilling/drill rig; Joides Resolution; Leg209; North Atlantic Ocean; Ocean Drilling Program; ODP |
| url | https://doi.org/10.1594/PANGAEA.707023 |